Braketed shooting

I have noticed some curious things about bracketed shooting. If you shoot an AE bracket, the camera is locked until all writing to the card is complete. The light remains orange and the message "storing" remains on the screen. If you shoot a normal burst, the light alternates between orange and green and it's possible to continue shooting while the write is being done. If you shoot any other type of bracketed shot, the images are only stored as jpegs, regardless of how you have the image quality set. Same is true for panoramas.

I don't understand why this is the case. It seems that if it will allow you to interupt the write while storing a burst, it should allow you to interupt the write while storing a bracketed burst. The bracketing performance also seems strange. I understand that film modes only apply to jpegs, so that make some sense, but the other bracketing modes apply to raw as well as jpegs, so it seems like I should have the option of shooting raw iso brackets or raw dr brackets. Panaramas, of course, are jpeg only.